The purpose of the proposed research is to estimate levels and trends in U.S. mortality in the last half of the nineteenth century. In addition to estimating levels and trends at a national level the proposed project will estimate mortality differentials for regions of the country, rural and urban areas, and nativity groups. The project will also examine the determinants of mortality levels and change during this period. Data on nutritional levels and the provision of public health provisions will be related to mortality conditions. Mortality data available in the federal census will be used in this research. This research will add to current knowledge on the demographic transition by clarifying the American experiece and by testing a number of theories of causation of the decline in mortality in the now developed world.